This invention relates to a fluid filter, such as a disposable-type, oil filter, and a method for attaching same in sealing relation to a filter mount on an engine.
The type of fluid filter now commonly used as an oil filter for motor vehicles is the "spin-on," disposable-type, because it is relatively inexpensive to mass produce and easy to install and replace. Such a spin-on, disposable-type, fluid filter is shown in FIG. 1 herein and is indicated generally by reference number 10. This filter 10 includes a housing 11 having a cylindrical side wall 12, a shaped closed end 14 for cooperation with a filter wrench (not shown), and an opposite, open end 15 covered with an end plate or wall 16 having oil flow openings 18 formed therein to allow oil to flow into the filter 10. An annular, resilient, sealing gasket 20 is retained in an annular channel 22 formed on the end wall 16 for cooperation with a flat sealing surface 24 of a filter mount 26 to which the filter 10 is attached. The filter mount 26 is formed on an engine 28 and also includes oil flow openings 34. Located centrally of the end wall 16 is a threaded aperture 30 which receives a threaded stud 32 carried by the filter mount 26.
During normal operation, flow of oil is from the engine 28, through the oil flow openings 34 formed in filter mount 26, into the oil flow openings 18 formed in the end wall 16, through an antidrain back and bypass valve (not shown), through the filter media 36, through the center tube (not shown), through the central aperture 30, into the hollow interior 38 of the stud 32 and back to the engine 28. In the "bypass" mode, the antidrain back and by pass valve causes the oil to bypass the filter media 36 and the center tube.
The common and continuing problems of this conventional spin-on, disposable filter are discussed below.
First, when the filter 10 is attached to the filter mount 26, friction, twisting, and compressive forces act on the sealing gasket 20 positioned between the end wall 16 and the filter mount 26. As a result, the sealing gasket 20 can become deformed or can be caused to lie "off-center" of the channel 22. In addition, the quality of the seal deteriorates with time and temperature aging of the sealing gasket 20 requires a high torque to remove the filter 10.
Second, the sealing gasket 20 is of the compression type where the hydraulic load works against the sealing surface 24 of the filter mount 26 and the performance of the sealing gasket 20 is a function of the stiffness of the end wall 16. Operational performance is worsened when the sealing gasket 20 is placed at the outer edge of the traditional end wall 16 because the hydraulic load acts to deflect and separate the filter mount sealing surface 24 from the end wall 16. Hence, the sealing gasket 20 must expand to fill this ever-increasing gap. One known technique for improving the strength of the sealing gasket 20 is to incorporate a peripheral, metal ring therein, as taught by co-assigned U.S. Pat. No. 4,473,471, issued to Robichaud et al., however, such a ring cannot fully compensate for this expansion.
Third, installation of the conventional filter 10 is not foolproof. The filter 10 should be torqued after the sealing gasket 20 contacts the filter mount 26; however, it is not possible to positively determine proper contact of the sealing gasket 20 in most conventional installations.
Fourth, due to the great pressures encountered during operation, it is necessary to manufacture the area of attachment of the filter 10 to the filter mount 26, i.e., the end wall 16, from a material whose thickness and strength can withstand these pressures. Of course, a filter design requiring a thick, strong material for the area of attachment results in high raw material and manufacturing costs.
Fifth, since conventional wisdom has counseled that the area of attachment should be at the center of the end wall in the form of corresponding threaded members, the means for sealing the space between the filter and the filter mount has necessarily been restricted to the area surrounding the corresponding threaded members. As a result, manufacturing design freedom and the efficiency of the sealing means has suffered.
Sixth, the total raw material cost of the filtration process components, i.e., filter media 36, related adhesives, etc., is less than a third of the total raw material cost of each filter 10. The remaining two-thirds of the cost is related to the non-filtration process components, i.e., the sealing gasket 20, end wall 16, etc. Due to this disproportional cost ratio, it is highly desired to minimize the cost of the non-filtration process components.
Seventh and finally, the conventional fluid filter 10 requires machining or cutting of various filter parts, such as the threaded stud 32 and central aperture 30. The goal of generating high volume production of fluid filters including thick end walls 16 having quality threads, i.e., without leaving traces of chips and burrs, has posed serious, longstanding problems in the industry.
Thus, it can be seen that the known fluid filters have fluid sealing problems, necessarily demand that relatively thick metal be used in the area of attachment, and are relatively expensive and difficult to manufacture. None of the known prior art fluid filters have the novel features of the invention disclosed herein which overcome these disadvantages.